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Added in API level 14

SynthesisCallback

public interface SynthesisCallback

android.speech.tts.SynthesisCallback


A callback to return speech data synthesized by a text to speech engine. The engine can provide streaming audio by calling start(int, int, int), then audioAvailable(byte[], int, int) until all audio has been provided, then finally done(). error() can be called at any stage in the synthesis process to indicate that an error has occurred, but if the call is made after a call to done(), it might be discarded. done() must be called at the end of synthesis, regardless of errors. All methods can be only called on the synthesis thread.

Summary

Public methods

abstract int audioAvailable(byte[] buffer, int offset, int length)

The service should call this method when synthesized audio is ready for consumption.

abstract int done()

The service should call this method when all the synthesized audio for a request has been passed to audioAvailable(byte[], int, int).

abstract void error(int errorCode)

The service should call this method if the speech synthesis fails.

abstract void error()

The service should call this method if the speech synthesis fails.

abstract int getMaxBufferSize()
abstract boolean hasFinished()

Check if done() was called or not.

abstract boolean hasStarted()

Check if start(int, int, int) was called or not.

abstract int start(int sampleRateInHz, int audioFormat, int channelCount)

The service should call this when it starts to synthesize audio for this request.

Public methods

audioAvailable

Added in API level 14
int audioAvailable (byte[] buffer, 
                int offset, 
                int length)

The service should call this method when synthesized audio is ready for consumption. This method should only be called on the synthesis thread, while in onSynthesizeText(SynthesisRequest, SynthesisCallback).

Parameters
buffer byte: The generated audio data. This method will not hold on to buffer, so the caller is free to modify it after this method returns.
offset int: The offset into buffer where the audio data starts.
length int: The number of bytes of audio data in buffer. This must be less than or equal to the return value of getMaxBufferSize().
Returns
int SUCCESS, ERROR or STOPPED.

done

Added in API level 14
int done ()

The service should call this method when all the synthesized audio for a request has been passed to audioAvailable(byte[], int, int). This method should only be called on the synthesis thread, while in onSynthesizeText(SynthesisRequest, SynthesisCallback). This method has to be called if start(int, int, int) and/or error() was called.

Returns
int SUCCESS, ERROR or STOPPED.

error

Added in API level 21
void error (int errorCode)

The service should call this method if the speech synthesis fails. This method should only be called on the synthesis thread, while in onSynthesizeText(SynthesisRequest, SynthesisCallback).

Parameters
errorCode int: Error code to pass to the client. One of the ERROR_ values from TextToSpeech

error

Added in API level 14
void error ()

The service should call this method if the speech synthesis fails. This method should only be called on the synthesis thread, while in onSynthesizeText(SynthesisRequest, SynthesisCallback).

getMaxBufferSize

Added in API level 14
int getMaxBufferSize ()

Returns
int the maximum number of bytes that the TTS engine can pass in a single call of audioAvailable(byte[], int, int). Calls to audioAvailable(byte[], int, int) with data lengths larger than this value will not succeed.

hasFinished

Added in API level 21
boolean hasFinished ()

Check if done() was called or not. This method should only be called on the synthesis thread, while in onSynthesizeText(SynthesisRequest, SynthesisCallback). Useful for checking if a fallback from network request is possible.

Returns
boolean

hasStarted

Added in API level 21
boolean hasStarted ()

Check if start(int, int, int) was called or not. This method should only be called on the synthesis thread, while in onSynthesizeText(SynthesisRequest, SynthesisCallback). Useful for checking if a fallback from network request is possible.

Returns
boolean

start

Added in API level 14
int start (int sampleRateInHz, 
                int audioFormat, 
                int channelCount)

The service should call this when it starts to synthesize audio for this request. This method should only be called on the synthesis thread, while in onSynthesizeText(SynthesisRequest, SynthesisCallback).

Parameters
sampleRateInHz int: Sample rate in HZ of the generated audio.
audioFormat int: Audio format of the generated audio. Must be one of ENCODING_PCM_8BIT or ENCODING_PCM_16BIT. Can also be ENCODING_PCM_FLOAT when targetting Android N and above.
channelCount int: The number of channels. Must be 1 or 2.
Returns
int SUCCESS, ERROR or STOPPED.
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